1. Field of the Invention
The present invention relates to an ink jet recorder having a purging device, and more particularly to an ink jet recorder having a purging device which is capable of effectively removing bubbles and foreign objects attached to wall surfaces of ink passages of a recording head.
2. Description of the Related Art
Generally, an ink jet printer, for example, is known as an ink jet recording apparatus for effecting recording such as printing by ejecting ink onto a recording medium such as paper.
In the ink jet printer, as shown in FIG. 11, an ink cartridge P1 in which ink is accommodated is replaceably mounted on a recording head unit P3 having a recording head P2. Ink is supplied from the replaced ink cartridge P1 to the recording head P2, and is ejected through ejection nozzles P4 so as to effect recording.
Further, such as in the course of using the ink jet printer, a so-called purging operation in which the ink is sucked from distal end sides of the ejection nozzles P4, i.e., from nozzle faces P5 where ejection holes (not shown) are open, is performed by the manual operation of a switch by a user or automatically when a predetermined condition has been met.
The purging operation is an operation in which a suction cap P6 is applied to the nozzle face P5, and negative pressure is applied to the interior of the suction cap P6 by a suction pump (not shown), thereby sucking the ink from inside the recording head P2 through the suction cap P6 and removing the same to outside.
However, there have been cases where very small bubbles and dust remaining inside ink passages cannot be removed sufficiently by only the purging operation based on the suction which makes use of the aforementioned negative pressure.
Namely, there has been a problem in that although very small bubbles and dust are sometimes attached to inner peripheral surfaces (wall surfaces) of unillustrated channels and a manifold for forming ink passages, since the closer to the wall surface, the slower the velocity of flow of the ink, it is difficult to remove the bubbles and dust attached to the wall surfaces even if flow of ink is produced by executing a purge.
If the bubbles and dust remain in the passages of the ink, there have been cases where ejection is hampered during the ejection of the ink, resulting in a decline in the recording quality.
Accordingly, as disclosed in Japanese Patent Application No. 295267/1988 and in its corresponding U.S. Pat. No. 5,298,923, a technique has been proposed in which the printing head is driven in synchronism with the suction of the ink in the purging operation. According to this technique, the ink in the ink passages is vibrated by driving the printing head, and very small dust and bubbles which are attached to the inner wall surfaces of the inner wall surfaces of the ink passages and which could not be removed by suction alone are also exfoliated smoothly and are easily removed by the vibration of the ink.
However, this publication fails to disclose the execution of the operation of the actuators of the print head after the lapse of a predetermined time duration from the start of the purging operation as in the present invention.
When a user has loaded an ink cartridge in a new printer for the first time in the use of the ink jet printer, the ink passages are filled with air. In addition, when the ink cartridge has been replaced, air is present between the ink cartridge and the print head. Further, after making a misjudgment that ejection is impossible when the remaining amount of ink has become small, the user might effect a purging operation to recover the ejecting function. If the user does so, there occurs a state in which the print head is emptied of the ink and the ink passages are filled with air.
If the ink is abruptly sucked by applying a large negative pressure at a stroke when filling the ink passages with the ink by performing a purging operation in the above-described state, the ink and air become mixed and flow into the print head, so that bubbling occurs in the ink, and the bubbles are entrained in the ink inside the print head. In particular, in a case where filter members are provided to prevent dust and the like from moving toward the print head together with the ink, when the ink abruptly passes through the filter members, large-scale bubbling occurs, and bubbles are produced in a large amount.
Thus, in the state in which a mixture of ink and air has abruptly flowed into the print head, if the print head is driven in synchronism with the suction of the ink as in the technique disclosed in the aforementioned publication, the bubbling of the ink is further prompted. As a result, the ejection of the ink is hampered appreciably, and it becomes impossible to effect normal printing.